Gas pressure monitor for pneumatic surgical machine

ABSTRACT

A gas pressure monitor system for a pneumatically-powered surgical machine includes a first transducer, a second transducer, and a controller. The first transducer is located upstream from a filter and is configured to read a first pressure of a gas before the gas enters the filter. The second transducer is located downstream from the filter and is configured to read a second pressure of a gas after the gas exits the filter. The controller is configured to compute a difference between the first pressure and the second pressure. A state of the filter is determined from the difference between the first pressure and the second pressure.

FIELD OF THE INVENTION

The present invention relates to a pneumatic module for a surgicalmachine and more particularly to a safety filter monitor for such amodule.

BACKGROUND OF THE INVENTION

Several conditions of the eye threaten sight. Epiretinal membrane (ERM),also known as macular pucker and cellophane retinopathy, is a conditioncharacterized by growth of a membrane across the macula, or centralretina of the eye. This condition may be thought of as the growth ofscar tissue across the macula, thus interfering with central vision. TheERM typically contracts, causing distortion of the central retina, thusproducing distortion of vision. Most patients will note that eitherstraight objects appear wavy and crooked and/or central vision isreduced, depending on the severity of the condition.

Epiretinal membranes may be associated with other conditions of the eye,however, the large majority are idiopathic, which means that the causeis unknown. Some of the disorders which are occasionally associated withERM's include previous retinal detachments and surgery thereof,inflammatory conditions (uveitis), retinal tears, and branch retinalvein occlusion (BRVO) and central retinal vein occlusion (CRVO).

Another condition is a macular hole. A macular hole is almost always aspontaneous development that occurs predominantly in aging women. Thedevelopment of a macular hole progresses through several stages, andwith each progressive stage the vision may worsen. It has beenpostulated that shrinkage of the vitreous humor may produce traction onthe fovea (central macula), thereby producing the hole itself. However,the cause of macular holes remains under investigation.

The retina, which lines the inside of the posterior wall of the eye, mayoccasionally become detached for various reasons. Most commonly, retinaldetachment occurs as a result of a tear or hole in the retina, whichdevelops as a result of a posterior vitreous separation (PVS). Theretinal tear or hole allows fluid to enter the subretinal space, thusdetaching the retina.

The retina receives oxygen and nutrients from the underlying choroid(vascular layer) of the eye. When a retinal detachment occurs, thedetached retina begins to dysfunction, and ultimately, necrosis (death)ensues as a result if the retina is not reattached to the underlyingchoroid. As such, a retinal detachment is an urgent condition. Thedetached retina should be recognized and treated promptly.

Vitreo-retinal procedures may be appropriate to treat these and otherserious conditions of the back of the eye. Vitreo-retinal proceduresinclude a variety of surgical procedures performed to restore, preserve,and enhance vision. Vitreo-retinal procedures treat conditions such asage-related macular degeneration (AMD), diabetic retinopathy anddiabetic vitreous hemorrhage, macular hole, retinal detachment,epiretinal membrane, CMV retinitis, and many other ophthalmicconditions.

The vitreous is a normally clear, gel-like substance that fills thecenter of the eye. It makes up approximately ⅔ of the eye's volume,giving it form and shape before birth. Certain problems affecting theback of the eye may require a vitrectomy, or surgical removal of thevitreous.

A vitrectomy may be performed to clear blood and debris from the eye, toremove scar tissue, or to alleviate traction on the retina. Blood,inflammatory cells, debris, and scar tissue obscure light as it passesthrough the eye to the retina, resulting in blurred vision. The vitreousis also removed if it is pulling or tugging the retina from its normalposition. Some of the most common eye conditions that require vitrectomyinclude complications from diabetic retinopathy such as retinaldetachment or bleeding, macular hole, retinal detachment, pre-retinalmembrane fibrosis, bleeding inside the eye (vitreous hemorrhage), injuryor infection, and certain problems related to previous eye surgery.

The retinal surgeon performs a vitrectomy with a microscope and speciallenses designed to provide a clear image of the back of the eye. Severaltiny incisions just a few millimeters in length are made on the sclera.The retinal surgeon inserts microsurgical instruments through theincisions such as a fiber optic light source to illuminate inside theeye, an infusion line to maintain the eye's shape during surgery, andinstruments to cut and remove the vitreous.

In a vitrectomy, the surgeon creates three tiny incisions in the eye forthree separate instruments. These incisions are placed in the pars planaof the eye, which is located just behind the iris but in front of theretina. The instruments which pass through these incisions include alight pipe, an infusion port, and the vitrectomy cutting device. Thelight pipe is the equivalent of a microscopic high-intensity flashlightfor use within the eye. The infusion port is required to replace fluidin the eye and maintain proper pressure within the eye. The vitrector,or cutting device, works like a tiny guillotine, with an oscillatingmicroscopic cutter to remove the vitreous gel in a slow and controlledfashion. This prevents significant traction on the retina during theremoval of the vitreous humor.

The surgical machine used to perform a vitrectomy and other surgeries onthe posterior of the eye are very complex. Typically, such an ophthalmicsurgical machine includes a main console to which numerous differenttools are attached. The main console provides power to and controls theoperation of the attached tools.

The attached tools typically include probes, scissors, forceps,illuminators, and infusion lines. Each of these tools is typicallyattached to the main surgical console. A computer in the main surgicalconsole monitors and controls the operation of these tools. These toolsalso get their power from the main surgical console. Some of these toolsare electrically powered while others are pneumatically powered.

In order to provide pneumatic power to the various tools, the mainsurgical console has a pneumatic or air distribution module. Thispneumatic module conditions and supplies compressed air or gas to powerthe tools. Typically, the pneumatic module is connected to a cylinderthat contains compressed gas. Most commonly, surgeons use cylinders ofnitrogen at 3600 psi. The condition and output of these cylinders affectthe operation of the surgical machine.

The proper gas pressure must be provided by the pneumatic module to thetools in order to insure their proper operation. Providing too low ortoo high a gas pressure can lead to safety problems. Too low a gaspressure can lead to underperformance or non-performance of theoperation of a tool. Too high a pressure can damage equipment or lead toa malfunction during surgery. In either case, the safety of the patientis compromised.

It would be desirable to incorporate a gas pressure monitor in anophthalmic surgical machine to protect the patient.

SUMMARY OF THE INVENTION

In one embodiment consistent with the principles of the presentinvention, the present invention is a gas pressure monitor system for apneumatically-powered surgical machine. The system includes a firsttransducer, a second transducer, and a controller. The first transduceris located upstream from a filter and is configured to read a firstpressure of a gas before the gas enters the filter. The secondtransducer is located downstream from the filter and is configured toread a second pressure of a gas after the gas exits the filter. Thecontroller is configured to compute a difference between the firstpressure and the second pressure. A state of the filter is determinedfrom the difference between the first pressure and the second pressure.

In another embodiment consistent with the principles of the presentinvention, the present invention is a gas pressure monitor system for apneumatically-powered surgical machine. The system includes a firsttransducer, a second transducer, a coupling, an isolation valve, apressure release valve, and four manifolds. The first transducer islocated upstream from a filter and is configured to read a firstpressure of a gas before the gas enters the filter. The secondtransducer is located downstream from the filter and is configured toread a second pressure of a gas after the gas exits the filter. Thecoupling is configured to accept gas from a gas source. The isolationvalve is located between the first transducer and the filter. Thepressure relief valve is located between the coupling and the firsttransducer. The first manifold fluidly connects the first transducer tothe isolation valve. The second manifold fluidly connects the isolationvalve to the filter. The third manifold fluidly connects the filter tothe second transducer. The fourth manifold fluidly connects the couplingand the pressure relief valve to the first transducer.

In another embodiment consistent with the principles of the presentinvention, the present invention is a gas pressure monitor system for apneumatic module. The system includes a first transducer, a secondtransducer, a coupling, an isolation valve, a pressure release valve,logic, and four manifolds. The first transducer is located upstream froma filter and is configured to read a first pressure of a gas before thegas enters the filter. The second transducer is located downstream fromthe filter and is configured to read a second pressure of a gas afterthe gas exits the filter. The coupling is configured to accept gas froma gas source. The isolation valve is located between the firsttransducer and the filter. The pressure relief valve is located betweenthe coupling and the first transducer. The first manifold fluidlyconnects the first transducer to the isolation valve. The secondmanifold fluidly connects the isolation valve to the filter. The thirdmanifold fluidly connects the filter to the second transducer. Thefourth manifold fluidly connects the coupling and the pressure reliefvalve to the first transducer. The logic is configured to compute adifference between the first pressure reading and the second pressurereading. When the difference between the first pressure reading and thesecond pressure reading is greater than a second amount, an indicationthat the filter needs service is provided. When the first pressurereading is greater than a first amount, the pressure release valve isopened and the isolation valve is closed. When the second pressure isless than a third amount, the isolation valve is closed.

In another embodiment consistent with the principles of the presentinvention, the present invention is a method for monitoring gas pressurein a pneumatic module of a surgical machine. The method includes sensinga first pressure of a gas upstream from a filter and sensing a secondpressure of a gas downstream from the filter. If the first pressure isgreater than a first amount, a pressure relief valve is opened, and anindication of high gas pressure is provided. If the second pressure isless than a second amount, an indication of low gas pressure isprovided.

In another embodiment consistent with the principles of the presentinvention, the present invention is a method for monitoring the state ofa filter in a pneumatic module of a surgical machine. The methodincludes sensing a first pressure of a gas upstream from a filter,sensing a second pressure of a gas downstream from the filter, computinga difference between the first pressure and the second pressure, andcomparing the difference to a value to determine a state of the filter.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the invention asclaimed. The following description, as well as the practice of theinvention, set forth and suggest additional advantages and purposes ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram of a pneumatically-powered ophthalmic surgerymachine according to an embodiment of the present invention.

FIG. 2 is a schematic of a gas pressure monitor system for apneumatically powered surgical machine according to an embodiment of thepresent invention.

FIG. 3 is a flow chart of one method of operation according to anembodiment of the present invention.

FIG. 4 is a flow chart of one method of operation according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are usedthroughout the drawings to refer to the same or like parts.

FIG. 1 is a block diagram of a pneumatically powered ophthalmic surgicalmachine according to an embodiment of the present invention. In FIG. 1,the machine includes gas pressure monitor system 110, proportionalcontroller 120, proportional controller 130, and tools 140, 150, 160,and 170. The tools 140, 150, 160, and 170 can be, for example, scissors,vitrectomy probes, forceps, and injection or extraction modules. Othertools may also be employed with the machine of FIG. 1.

As shown in FIG. 1, gas pressure monitor system 110 is fluidly coupledvia a manifold to proportional controller 120 and proportionalcontroller 130. A single manifold may connect gas pressure monitorsystem 110 to proportional controller 120 and proportional controller130, or two separate manifolds may connect gas pressure monitor system110 to proportional controller 120 and proportional controller 130,respectively. Proportional controller 120 is fluidly coupled to tools140 and 150 by, for example, a manifold and tubing. Likewiseproportional controller 130 is fluidly coupled to tools 160 and 170, by,for example, a manifold and tubing.

In operation, the pneumatically powered ophthalmic surgery machine ofFIG. 1 operates to assist a surgeon in performing various ophthalmicsurgical procedures, such as a vitrectomy. A compressed gas, such asnitrogen, provides the power for tools 140,150, 160, and 170. Thecompressed gas passes through gas pressure monitor system 110, throughone or more manifolds to proportional controllers 120 and 130, andthrough additional manifolds and/or tubing to tools 140, 150, 160, and170.

Gas pressure monitor system 110 functions to monitor the pressure ofcompressed gas from a gas source as it enters the machine. As furtherdiscussed below, gas pressure monitor system acts to ensure the safetyof the operation of the machine.

Proportional controllers 120 and 130 serve to distribute the compressedgas received from gas pressure monitor system 110. Proportionalcontrollers 120 and 130 control the pneumatic power delivered to tools140, 150, 160, and 170.

Tools 140, 150, 160, and 170 are all pneumatically powered. In such acase, compressed gas powers the operation of these tools. Variousvalves, manifolds, and tubing are used to direct compressed gas from gaspressure monitor system 110, through proportional controllers 120 and130, and into tools 140, 150,160, and 170. This compressed gas actuatescylinders, for example, in tools 140, 150, 160, and 170.

FIG. 2 is a schematic of a gas pressure monitor system for apneumatically powered surgical machine according to an embodiment of thepresent invention. In FIG. 2, the gas pressure monitor system includes agas source 205, coupling 210, manifold 215, pressure release valve 220,first transducer 225, second transducer 230, isolation valve 235, filter240, manifold 245, controller 250, manifold 255, interface 260, manifold265, interface 270, and interface 275. While all of these components aredepicted in FIG. 2 as being of part of gas pressure monitor system 110,a subset of these components may comprise gas pressure monitor system110 as described in the appended claims.

In the embodiment of FIG. 2, gas source 205 is fluidly coupled throughcoupling 210 to manifold 215. Manifold 215 fluidly couples pressurerelease valve 220, coupling 210, and first transducer 225. In thismanner, a single manifold connects gas source 205 to first transducer to225 and pressure release valve 220.

First transducer 225 is fluidly coupled to isolation valve 235 viamanifold 245. Isolation valve 235 is fluidly coupled to filter 240 viamanifold 255. Filter 240 is fluidly coupled to second transducer 230 viamanifold 265.

Controller 250 receives signals from first transducer 225 via interface260 and from second transducer 230 via interface 270. In this manner,first transducer 225 is electrically coupled to controller 250 viainterface 260. Second transducer 230 is electrically coupled tocontroller 250 via interface 270. Interface 275 is an output ofcontroller 250. In this example, interface 275 carries output signalsfrom controller 250 to other components of gas pressure monitor system110 such as isolation valve 235 and pressure release valve 220.

The gas pressure monitor system 110 of FIG. 2 includes gas source 205.Gas source 205 is typically a bottle or cylinder of compressed gas. Inmany cases, surgeons utilize cylinders of compressed nitrogen. In othercases, surgeons utilize a source of compressed air. In either case, gassource 205 is a source of compressed gas that provides the pneumaticpower for the pneumatically powered ophthalmic surgery machine.

Coupling 210 is an input port that receives compressed gas from gassource 205. In most cases, coupling 210 is a standard connector on amanifold designed to connect to tubing from gas source 205. Coupling 210allows compressed gas from gas source 205 to enter gas pressure monitorsystem 110 and provide pneumatic power to the machine.

Pressure release valve 220 is a valve configured to open if the pressurein manifold 215 is too high. In this manner, pressure release valve 220operates to release compressed gas from manifold 215 if the pressure ofthat compressed gas exceeds a certain threshold. In many cases, pressurerelease valve 220 has a set point that can be adjusted. For example,pressure release valve 220 may have a user adjustable set point. In sucha case, an engineer may be able to set the set point at 200 lbs persquare inch (psi), and pressure release valve 220 opens when thepressure of the compressed gas in manifold 215 exceeds 200 psi. In otherembodiments consistent with the present invention, pressure releasevalve 220 is controlled by controller 250. In such a case, controller250 maybe able to send electrical signals via interface 275 tocontroller pressure release valve 220.

In the embodiment of FIG. 2, isolation valve 235 is a standard two wayvalve. In this case, isolation valve 235 has two positions—on and off.When isolation valve 235 is turned on, gas is allowed to flow frommanifold 245 to manifold 255. When isolation valve 235 is turned off,gas is not allowed to flow from manifold 245 to manifold 255. In theembodiment of FIG. 2, isolation valve 235 is depicted as being turnedoff. Isolation valve 235 maybe controlled by controller 250. In thismanner, controller 250 sends signals via interface 275 to isolationvalve 235 to control its operation. For example, controller 250 may senda signal via interface 275 to isolation valve 235 to turn it to an onposition.

In the embodiment of FIG. 2, filter 240 serves to filter compressed gaspassing from manifold 255 to manifold 265. Filter 240 also acts as awater separator. In this manner, filter 240 serves to filter objectsfrom the compressed gas as it passes from manifold 255 to manifold 265.Filter 240 also serves to remove water from the compressed gas as itpasses from manifold 255 to manifold 265. In the embodiment of FIG. 2,filter 240 filters the compressed gas before it enters the remainder ofthe machine.

First transducer 225 and second transducer 230 operate to read anatmospheric pressure of the gas contained in manifold 215 and manifold265 respectfully. In this manner, first transducer 225 reads thepressure of the compressed gas after it exits gas source 205, enterscoupling 210, and enters manifold 215. Likewise, second transducer 230reads the pressure of the compressed gas as it exits filter 240 andenters manifold 265. In other words, first transducer 225 reads thepressure of the compressed gas that is located in the manifold adjacentto first transducer 225. Likewise, second transducer 230 reads thepressure of the compressed gas that is adjacent to it in manifold 265.

In the embodiment of FIG. 2, first transducer 225 and second transducer230 are common pressure transducers. First transducer 225 and secondtransducer 230 are capable of reading pressure of a compressed gas andsending an electrical signal containing information about the pressureof the compressed gas to controller 250. First transducer 225 sends asignal corresponding to the pressure of the compressed gas that it readsvia interface 260. Likewise, second transducer 230 sends a signal aboutthe pressure of the compressed gas via interface 270 to controller 250.

Controller 250 is typically an intergraded circuit capable of performinglogic functions. Controller 250 is typically in the form of a standardintergraded circuit package with power, input, and output pins. Invarious embodiments, controller 250 is a valve controller or a targeteddevice controller. In such a case, controller 250 performs specificcontrol functions targeted to a specific device, such as a valve. For anexample, a valve controller has the basic functionality to control avalve. In other embodiments, controller 250 is a microprocessor. In sucha case, controller 250 is programmable so that it can function tocontrol valves in gas pressure monitor system 110 as well as othercomponents of the machine. In other cases, controller 250 is not aprogrammable microprocessor, but instead is a special purpose controllerconfigured to control different valves that perform different functions.

Controller 250 is configured to receive signals from first transducer225 via interface 260 and from second transducer 230 via interface 270.These signals, for example, correspond to readings of gas pressure inmanifold 215 and manifold 265, respectively. Controller 250 is alsoconfigured to send output signals via interface 275. As noted, theseoutput signals from controller 250 are typically sent to valves, such asisolation valve 235, via interface 275.

Manifolds 215, 245, 255, 265 are all configured to carry compressed gas.In the embodiment of FIG. 2, these manifolds are machined out of ametal, such as aluminum. These manifolds are air tight, contain variousfittings and couplings, and are designed to withstand relatively highgas pressures. These manifolds maybe manufactured as individual piecesor they maybe manufactured as a single piece. For example, manifold 215and manifold 245 maybe a single continuous manifold. In this manner,manifold 215 and manifold 245 are machined from a single piece ofaluminum. In such a case, one end of manifold 215 and manifold 245 isdesigned to house coupling 210, another end is designed to housepressure release valve 220, another end is designed to accommodateisolation valve 235, and another end is designed to accommodate firsttransducer 225.

Interface 260 and interface 270 are designed to carry signals from firsttransducer 225 and second transducer 230 to controller 250. In thiscase, interface 260 and interface 270 are common electrical conductorssuch as wires. Likewise, interface 275 carries signals from controller250 to isolation valve 235, for example. Interface 275 maybe one or morewires or buses designed to carry electrical or data signals.

The gas pressure monitor system 110 of FIG. 2 provides compressed gas tothe remainder of a surgical machine. In operation, compressed gas fromgas source 205 passes through coupling 210 and into manifolds 215 and245. First transducer 225 reads the pressure of the compressed gas inmanifolds 215 and 245. Compressed gas is also allowed to travel frommanifolds 215 to the input of pressure release valve 220. As depicted inFIG. 2, pressure release valve 220 is turned off. Therefore, thepressure of compressed gas is allowed to maintain itself in manifolds215 and 245. Isolation valve 235 is also turned off.

First transducer 225 reads the pressure of the compressed gas inmanifold 215 and 245. If the pressure of the compressed gas is toogreat, pressure release valve 220 opens and allows the compressed gas tovent to the atmosphere. If the pressure of the compressed gas inmanifolds 215 and 245 is too low, then isolation valve 235 remains inthe closed or off position. In this manner, first transducer 225 reads apressure of the compressed gas after it enters gas pressure monitorsystem 110. If the pressure is too high, pressure release valve 220 isopened. If the pressure is too low, isolation valve 235 remains closedto prevent the low pressure gas from entering the remainder of thesystem. If the pressure of the compressed gas is within an acceptablerange, then isolation valve 235 is opened and the compressed gas isallowed to pass into manifold 255, through filter 240, and into manifold265.

When the compressed gas enters manifold 265, second transducer 230measures the pressure of that gas. First transducer 225 measures thepressure of the compressed gas in manifolds 215 and 245 and sends asignal corresponding to this pressure via interface 260 to controller250. Likewise, second transducer 230 measures the pressure of thecompressed gas in manifold 265 (after it has passed through filter 240)and sends a signal corresponding to this pressure via interface 270 tocontroller 250. Controller 250 compares the pressure read by firsttransducer 225 to the pressure read by second transducer 230. Forexample, controller 250 may calculate a difference between the pressureread by second transducer 230 and the pressure read by first transducer225. This difference corresponds to a pressure drop across filter 240.

In some cases, as filter 240 wears, it becomes less efficient attransferring compressed gas. In such a case, the pressure read by thefirst transducer 225 is higher than the pressure read by secondtransducer 230. This means that a pressure drop has occurred acrossfilter 240. As filter 240 becomes more worn or more dirty, the pressureof the compressed gas in manifold 265 as read by second transducer 230may drop to a level that is too low to safely operate the machine. Insuch a case, filter 240 needs to be replaced or serviced. In thismanner, first transducer 225 and second transducer 230 serve to monitora state of filter 240. If the state of filter 240 is such that it needsto be serviced or replaced, then controller 250 may provide anindication in the form of illuminating a light emitting diode on asurgical console to indicate that filter 240 needs to be replaced orserviced. In addition, if the pressure read by second transducer 230falls below a safe level, then controller 250 may turn isolation valve235 off.

The gas pressure monitor system 110 of FIG. 2 implements various safetyfeatures in the ophthalmic surgery machine of FIG. 1. The first of thesefeatures is to cause high pressure compressed gas to be vented viapressure release valve 220 so that it does not damage the rest of thesurgical machine. In addition, venting high pressure compressed gas viapressure release valve 220 helps to prevent injury to the patient. Inthis case, if compressed gas with too high of pressure were allowed toenter the remainder of the surgical machine, the tools 140, 150, 160,and 170 may malfunction and injure a patient. In addition, the highpressure compressed gas may damage various components of the surgicalmachine. Therefore, if controller 250 receives a signal indicating thatthe pressure of the compressed gas in manifolds 215 and 245 is above asafe level, then controller 250 opens pressure release valve 220.Alternatively, pressure release valve 220 may be set at a set pointequal to the upper limit of a safe range of pressure for compressed gas.In such a case, if the pressure of the compressed gas in manifold 215exceeds the set point, pressure release valve 220 opens.

The gas pressure monitor system 110 of FIG. 2 also prevents theintroduction of compressed gas with too low a pressure into theremainder of the surgical machine. In this case, first transducer 225senses that the compressed gas in manifold or manifold 245 is at too lowa pressure. First transducer 225 sends a signal via interface 260 tocontroller 250 indicating such. Controller 250 receives this signal andcauses isolation valve 235 to remain closed. In this manner, compressedgas in manifold 245 is not allowed to pass into manifold 255 and theremainder of the machine. If the pressure of the compressed gas is toolow, then the surgical machine may not operate properly. For example, ifthe pressure of the compressed gas is too low, then the pneumatic powerprovided to tools 140, 150, 160, and 170 may not be sufficient to safelyoperate them. In such a case, the unsafe operation of these tools mayinjure the patient.

The gas pressure monitor system 110 of FIG. 2 also allow for theconstant monitoring of the state of filter 240. In this case, firsttransducer 225 and second transducer 230 act in tandem to monitor thecondition of filter 240. If filter 240 were to become clogged, forexample, then the surgical machine may not be operated safely. In such acase, controller 250 receives signals from first transducer 225 andsecond transducer 230 indicating this unsafe condition. In addition,first transducer 225 and second transducer 230 can constantly monitorthe condition of filter 240 to ensure that it is operating properly. Insuch a case, controller 250 may provide an indication that filter 240may need to be repaired or replaced. Typically, a pressure reading bysecond transducer 230 of the compressed gas in manifold 265 (after ithas passed through filter 240) provides an indication of the state ofthe filter 240. In one case, second transducer 230 may determine thatthe pressure of the compressed gas in manifold 265 is below a safelevel. In such a case, controller 250 may close or turn off theisolation valve 235. This prevents the low pressure compressed gas fromentering the remainder of the machine and causing unsafe operation.

FIG. 3 is a flow chart of one method of operation according to anembodiment of the present invention. In FIG. 3, a first pressure of agas upstream from a filter is sensed in 305. In 310, a second pressureof a gas downstream from the filter is sensed. In 315 a determination ismade as to whether the first pressure is greater than a first amount. In315, if the first pressure is greater than a first amount, then in 320,a pressure relief valve is opened. In 330 an indication of high gaspressure is provided. If the first pressure is not greater than a firstamount in 315, then in 335 a determination is made as to whether thesecond pressure is less than the second amount. An indication of low gaspressure is provided in 345. If the second pressure is not less than asecond amount in 335, then an isolation valve is opened in 350. Afterthe isolation valve is opened in 350, the process returns to 305 and afirst pressure of a gas upstream from a filter is sensed.

In the embodiment of FIG. 3, the gas pressure monitor system 110 sensesa first gas pressure on one side of a filter and a second gas pressureon the other side of the filter. If the first gas pressure upstream fromthe filter is greater than a safe amount, then the pressure releasevalve is open to vent the high pressure gas. If the second pressurereading, corresponding to the gas pressure downstream from the filter isless than a safe amount, then the isolation valve remains in the closedposition thus preventing the low pressure gas from reaching theremainder of the system and possibly causing an unsafe condition. In theembodiment of FIG. 3, gas pressure monitor system serves to ensure thatthe pressure of the compressed gas entering of the ophthalmic surgicalmachine is within a safe range.

FIG. 4 is a flow chart of another method of operation according to anembodiment of the present invention. In 405, a first pressure of a gasupstream from a filter is sensed. In 410, a second pressure of a gasdownstream from the filter is sensed. In 415, the difference between thefirst pressure and the second pressure is computed. In 420, adetermination is made as to the pressure drop across the filter. In 420,if the pressure drop across the filter is acceptable, then in 425 anisolation valve is opened. In 430, a determination is made as to whetherthe filter needs service. For example, this determination can be basedon the difference between the first pressure and the second pressurecomputed in 415. If the filter needs service in 430, then in 435 anindication that the filter needs service is provided. In 430, if thefilter does not need service, then the process returns to 405, and afirst pressure of a gas upstream from a filter is sensed.

In 420, if the pressure drop across the filter is not acceptable, thenin 445, an indication of low gas pressure is provided. In 450, andindication that the filter needs service is provided.

In the embodiment of FIG. 4, the first pressure reading and the secondpressure reading are used to determine a state of the filter. Inaddition, these pressure readings also determine an unsafe condition forthe surgical machine. The difference between the first pressure(upstream from the filter) and the second pressure (downstream from thefilter) corresponds to a pressure drop across the filter. If thepressure drop across the filter is too great, this indicates that thefilter needs to be replaced or serviced. In one case, if the filter isclogged, then the pressure drop across the filter can be very greatleading to an unsafe operation of the machine. The gas pressure monitorsystem 110 of the present invention thus ensure the safe operation ofthe machine and also ensures that a patient will not be harmed by theoperation of the machine with an unsafe gas pressure.

From the above, it may be appreciated that the present inventionprovides an improved system and methods for monitoring the gas pressurein a pneumatic module of a surgical machine. The present inventionprovides safety features designed to protect the patient and thesurgical machine from harm due to high or low gas pressure. In addition,the present invention provides a system for monitoring a filtercomponent of the pneumatic module. The present invention is illustratedherein by example, and various modifications may be made by a person ofordinary skill in the art.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A gas pressure monitor system for apneumatically-powered surgical machine comprising: a first transducerlocated upstream from a filter, the first transducer adapted to read afirst pressure of a gas before the gas enters the filter; a secondtransducer located downstream from the filter, the second transduceradapted to read a second pressure of a gas after the gas exits thefilter; a controller adapted to compute a difference between the firstpressure and the second pressure; and an isolation valve coupled to afluid pathway that includes the first transducer, second transducer, andfilter; wherein the controller is adapted to determine a state of thefilter from the difference between the first pressure and the secondpressure; wherein the controller is adapted to close the isolation valveunless: a) the first pressure is within a selected range of pressures;and b) the second pressure is greater than a selected pressure.
 2. Thesystem of claim 1 wherein the controller is adapted to indicate a needfor a filter service when the difference between the first pressure andthe second pressure is greater than the predetermined amount.
 3. Thesystem of claim 1 wherein the isolation valve is fluidly coupled to thefirst transducer via a manifold.
 4. The system of claim 2 wherein thecontroller is adapted to indicate a need for a filter service byilluminating a light emitting diode.
 5. The system of claim 1 whereinthe controller is further adapted to determine a useful life of thefilter using the difference between the first pressure and the secondpressure.
 6. The system of claim 1, further comprising a pressure reliefvalve upstream of the filter.
 7. The system of claim 6, wherein thecontroller is configured to open the pressure relief valve if the firstpressure is greater than a first amount.
 8. The system of claim 6,wherein the pressure relief valve is selectable between one of an opencondition and a closed condition, the relief valve in the open conditionwhen the first pressure meets or exceeds a selected pressure and therelief valve in the closed position when the first pressure is less thanthe selected pressure.
 9. A gas pressure monitor system for apneumatically-powered surgical machine comprising: a filter; a firsttransducer located upstream from the filter, the first transducerconfigured to read a first pressure of a gas before the gas enters thefilter; a second transducer located downstream from the filter, thesecond transducer configured to read a second pressure of a gas afterthe gas exits the filter; an isolation valve coupled to a fluid pathwaythat includes the first transducer, second transducer, and filter; and acontroller adapted to receive the first pressure from the firsttransducer and the second pressure from the second transducer andcompute a pressure difference between the first pressure and the secondpressure, the controller further adapted to close the isolation valvewhen the pressure difference is above a selected pressure difference.10. The gas pressure monitor system of claim 9, wherein the controlleris further adapted to indicate a state of the filter from the differencebetween the first pressure and the second pressure.
 11. The system ofclaim 9, further comprising a pressure relief valve upstream of thefilter.
 12. The system of claim 11, wherein the controller is adapted toopen the pressure relief valve if the first pressure is greater than aselected pressure.